Dual extensible reach truck

ABSTRACT

An extensible mechanism for reach trucks in which the mechanism has an extensible and retractable vertical member pivotally attached to the rear portion of the vehicle for pivoting forwardly and rearwardly, a boom connected to the upper end of the vertical member and extending forwardly for supporting a load attachment such as a fork, and an extensible and retractable member spaced forwardly from the vertical member for supporting and pivoting the boom. Power cylinders are preferably used to extend and retract the two extensible and retractable members, and a power means is provided for pivoting the vertical member forwardly and rearwardly. The two extensible members may be moved in unison to lift the boom vertically on a plane, or one of the members may be moved while the other remains stationary, or they may be moved at different rates in order to lift, move and place a load on the boom attachment in a desired location. Either single or multiple extensible and retractable vertical and power members may be used to control the operation of the boom.

United States Patent [1 1 Holtkamp I [111 3,802,589 Apr. 9, 1974 [75] Inventor:

[52] US. Cl. 214/770, 214/146.5

[51] Int. Cl 1366f 9/00 [58] Field of Search 214/133, 141, 148, 770, 214/771; 212/46 B, 57, 64,, 59 R [56] References Cited UNITED STATES PATENTS 3,432,050 3/1969 Tendressee 214/770 2,788,139 4/1957 Tendressee 214/148 560,086 5/1896 Dobkins 212/57 3,024,933 3/1962 Albert et a1 214/770 3,338,438 8/1967 Holtkamp 314/302 3,288,316 11/1966 West r 214/771 3,410,433 11/1968 Brown 214/771 Primary Examiner-Gerald M. Forlenza Assistant ExaminerLawrence .1. Oresky Attorney, Agent, or Firml-lobbs & Green [57] ABSTRACT An extensible mechanism for reach trucks in which the mechanism has an extensible and retractable vertical member pivotally attached to the rear portion of the vehicle for pivoting forwardly and rearwardly, a boom connected to the upper end of the vertical member and extending forwardly for supporting a load attachment such as a fork, and an extensible and retractable member spaced forwardly from the vertical member for supporting and pivoting the boom. Power cylinders are preferably used to extend and retract the two extensible and retractable members, and a power means is provided for pivoting the vertical member forwardly and rearwardly. The two extensible members may be moved in unison to lift the boom vertically on a plane, or one of the members may be moved while the other remains stationary, or they may be moved at different rates in order to lift, move and place a load on the boomattachment in a desired location. Either single or multiple extensible and retractable vertical and power members may be used to control the operation of the boom.

11 Claims, 5 Drawing Figures PATENIEDAPR 919M 3.802 589 SHEEI 3 [IF 4 FIG. 3

DUAL EXTENSIBLE REACH TRUCK ment to the scaffold platform or other work supporting structure. This type of truck has the further special advantage of being able to pick up a load immediately in front of the truck where the ground is firm, transport the load to the' work site, and deliver it to the scaffolding platform or partially completed building and yet avoid driving onto the usual soft backfill around the outside of the building. The extended reach trucks of the standard or well known construction utilize a parallelogram arrangement for the members supporting the forwardly extending support or boom, with the members pivoted to one another and to the truck frame. Movement of the members forwardly to a point approaching the fully extended-position result in a dropping of the forward end of the support, thus causing difficulty in locating the'load at the desired level and maintaining it at that level while advancing the load until it is positioned onto the scaffold platform or other work support. Further, the problem caused by the failure of the prior extended reach trucks to advance the load on a-horizontal plane, particularly as the load approached its fully extended position, was compounded by the effect of heavy loads and the weight of the conventional upright compressing the tires on the front wheel adjacent the load attachment, and by the dip caused by soft ground traversed by those wheels as the truck approached the place where the load was to be discharged. While movement of the load on a horizontal plane would not eliminate the difficulty caused by the load on the tires of soft ground, it would result in easier and more effective control of the extended reach mechanism and load attachment under those adverse conditions. It is therefore one of the principal objects of the present invention to provide an extended reach truck having a boom structure in which the boom is pivoted at its rear end to extensible posts and is supported midway by an extensible power means, thus permitting the boom to be lifted and lowered and extended and retracted on a plane, thereby providing good maneuverability and maximum reach of the boom at various load pick up and discharging levels.

Conventional extensible lift trucks have an upright mounted on the front, and this upright is relatively heavy and has two or more vertical tracks and cross members and operating cylinders which obscure the view of the operator. It is therefore another object of the invention to provide an extensible reach truck mechanism which does not require an upright to lift a load to the desired height, and which is so constructed and designed that the principal weight of the truck and reach mechanism is near the end of the vehicle opposite the load lifting end, thus effectively counterbalancing the load during the lifting and maneuvering operations.

Another object of the invention is to provide a truck having-an extended reach mechanism which has the ability to pick up a load below ground level, and which can be. controlled either manually or automatically to compensate for compression of the truck tires by the load or downwardly or upwardly tilting of the forward end of the truck as a result of the terrain, to obtain movement of the load on the horizontal plane under those conditions.

Still another object of the invention is to provide a material handling truck having an extended load mechanism of the aforesaid type which is so constructed and designed that it has maximum stability in all load handling positions and can be adapted to various types of truck designs without any appreciable modifications in the basic structure of the mechanism. 7

Further objects and advantages of the present invention will become apparent from the following description and accompanying drawings, wherein:

FIG. 1 is a perspective view of an extended reach truck embodying the present invention and showing the extended reach mechanism in its lowered position in full lines and in an elevated position in broken lines;

FIG. 2 is a side elevational view of the present lift truck showing the extended reach mechanism in its lowered and elevated positions;

FIG. 3 is a front elevational view of the truck shown in FIGS. 1 and 2;

FIG. 4 is a rear elevational view of the truck shown in the'preceding figures; and

FIG. 5 is a schematic diagram of the operating system of the extended reach mechanism.

Referring more specifically to the drawings, numeral 10 indicates generally a lift truck on which the present extended reach mechanism 12 is mounted, the truck having front drive wheels 14 and 16 and rear steerable wheels 18 and 20. While only the front wheels are driven and the rear wheels are steerable, the truck may be one in which the front and rear wheels are steerable and in which both sets of wheels are drive wheels. The motor driving the truck and providing the power for operating the extended reach mechanism is under hood cover 22 and is mounted on frame24, and the truck is controlled by an operator from cab 26 wherein the manual controls shown in FIG. 5 are located. While the extended reach mechanism may be mounted on various types of trucks and truck frames, the one shown has two longitudinal side members and a plurality of cross members formingthe support for the motor, controls and cab, and also forming the basic support for the extended reach mechanism. Various changes in the truck structure can be made to adapt it to the desired operation to be performed thereby.

The extended lift mechanism 12 includes a pair of posts 30 and 32 normally assuming a substantially upright position and being pivotally mounted on a shaft 34 secured to the rear end of frame 24 by mounting fixture 36. The two posts are rigidly joined to one another by a steel plate 38 to form a bifurcated structure which is adapted to tilt forwardly and rearwardly on the two pivot means 40 and 42, respectively, at opposite ends of shaft 34. Boom or arm 44 consisting of two longitudinal members 45 and 46 is pivotally connected to the upper ends of posts 30 and 32, respectively, and extends forwardly therefrom parallel to the sides of frame 24, the two members being adapted to pivot on the upper ends of the posts from a position such as that shown in solid lines in FIG. 2 to an elevated position shown in broken lines. Arm member 45 is pivotally connected to the upper end of post 30 by a shaft 48, and arm member 46 is pivotally connected to the upper end of post 32 by a shaft 50. A plurality of cross members 52 tie the two arm members together so that they operate in unison in moving loads from one position to another, both forwardly and rearwardly and up and down. Joined to the forward end of the arms and forming a part thereof are extensions 54 and 56 joined rigidly at one end to the main portion of the arms and pivotally supporting a load attachment 60 at the other end. Pivot pins 62 and 64 connect the forward end of the extensions to fixtures 66 and 68, respectively, on the attachment. The load attachment, which may be considered conventional for the purpose of the present description, is shown as a fork lift, and is moved to various angular positions by a suitable power mechanism such as a hydraulic cylinder 76. The fork attachment is provided with two spaced forks 77 and 78 rigidly connected to and supported by body or back structure 79.

Posts and 32 are of a telescopic construction, i.e., are extensible and contractable between the contracted position shown in full lines in FIG. 2 and the extended position shown in phantom in the same figure, the posts each having a conventional hydraulic cylinder assembly 80, consisting of an external cylinder 81, and a piston and piston rod 84 and 86, respectively, the latter being connected to the rear end of the boom 44. Posts 30 and 32 are pivoted forwardly and rearwardly on pivots 40 and 42 by cylinder assemblies 90 on opposite sides of the truck, which are connected at one end to frame 24 by fixtures 92, and connected at the other end through the piston rod 93 to pivot means 94, the two hydraulic cylinders being operated together from the same hydraulic system. Boom 44 is raised and lowered and pivoted relative to posts 30 and 32 by a pair of extensible and contractable legs 96 and 98, each consisting of hydraulic cylinder assemblies 100, the lower end.

of each cylinder being connected to the frame by a fixture 102 and the upper end through piston rod 103 to the arm members by a fixture 104. Fixture 104 for the upper end of cylinder assembly 100 is spaced further from pivot 48 than fixture 102 for the lower end of the assembly is from pivot means 40. Movement of the hydraulic mechanism in the two posts 30 and 32 moves the rear end of the boom upwardly or downwardly, causing the fixture 104 to which hydraulic cylinders 100 are connected to function as the fulcrum for the boom. The hydraulic cylinder 76, which is pivoted to extension 54 by a fixture 112 and to one of the side members of the upright by a fixture 114, may be operated from the hydraulic system of the truck as part of the system which operates the hydraulic cylinders of the extended reach mechanism, or by a separate hydraulic system, as described.

The hydraulic system for operating cylinder assemblies 80, 90 and 100 is shown schematically in FIG. 5, numeral 118 indicating generally the portion of the system controlling cylinder 80 in the posts, numeral 120 indicating generally the portion of the system controlling the cylinder 90, and numeral 122 indicating generally the portion of the system controlling cylinder 100. System 120 is connected to hydraulic pump 124 which delivcrcs oil from a tank or sump 126 through linel28 to a valve 130. The valve is connected to the cylinder on opposite sides of piston 132 by lines 134 and 136, and line 128 is connected through the valve to the sump byline 138. Line 128 is also connected to the valve by a branch line 140 which has a check valve 142 therein, and the return line for the valve is connected to line 138 and to the sump by a line 144. When post 30 is to be moved forwardly, i.e., to the left as illustrated in FIG. 5, the valve is moved downwardly as viewed in the drawing, thus connecting branch line 140 with line 136 and line 134 with line 144, thus causing piston 132 and piston rod 93 to move to the left, as viewed in FIG. 5, and to swing post 30 forwardly. When the post is to be moved in the opposite direction, the valve is moved upwardly as viewed in the drawing, thus connecting line 142 with line 134 and line 136 with line 144. After the post has been moved to the desired position, the valve is returned to its centered position where the valve permits hydraulic fluid to pass therethrough. A pressure relief valve indicated generally by numeral connects line 128 with line 138, thus limiting the maximum pressure in line 128 for operating the piston when the pump is in operation.

Hydraulic system 122 is connected to pump 124 by line 128, which is an extension of line 128. Line 128' is connected to valve 158 by a branch line 160 containing a check valve 161, and to the return line 138 by a line 162 when the valve is in its centered position. The valve is connected to cylinder 100 by lines 164 and 166. When boom 44 is to be raised by legs 96 and 98, the valve 158 is moved upwardly, as viewed in FIG. 5, thus connecting branch line 160 with line 164 and with the cylinder on the under side of piston 168, and connecting line 166 with return line 169, thus causing piston rod 103 to move the arm upwardly. When the boom is to be lowered, the valve is moved downwardly, connecting branch line 160 with line 166 and line 164 with return line 169. Since system 122 depends on valve 130 being in its neutral position for operation, valve 158 cannot control cylinder 100 while valve 130 is being controlled to operate cylinder 90, since movement of the latter valve in either direction disrupts the flow of fluid to valve 158.

Hydraulic system 118 which controls the operation of hydraulic cylinder assembly 80 consists of a valve connected to sump 126 or other suitable source of hydraulic fluid, by pressure line 182 and pump 184 and return line 186. A pressure relief valve 188 connects lines 182 and 186, thus limiting the maximum pressure in line 182 for operating the cylinder 82. The valve, which is shown as operated manually by a lever 189, is connected to the cylinder on opposite sides of piston 84 by lines 190 and 192. When the rear end of the boom is to be elevated, the valve is moved downwardly as viewed in FIG. 5, thus connecting lines 182 and 192 with the lower part of the cylinder assembly belowpiston 84, thus causing piston 84 to move upwardly and to pivot the boom on the fulcrum provided by fixture 104 at the upper ends of cylinder assemblies 100. When he rear end of the boom is to be lowered, the valve is moved upwardly as viewed in the drawings, thus connecting the upper part of the cylinder above piston 84 with return line 182, and the lower part of the cylinder line 186.

Cylinder assembly 100 may be held in a stationary position while cylinder assembly 80 is operated to tilt the boom upwardly or downwardly, and hence move the attachment 60 downwardly or upwardly, or the two cylinder assemblies 80 and 100 may be operated simultaneously to lift or lower the boom while maintaining the boom at a flxed angular position. In this operation, the two hydraulic assemblies 80 and 100 operate to raise the load directly upwardly or downwardly without attachment can be lowered to a point beneath the ground level on which the truck rests, and it can be retracted or advanced at various levels for raising and discharging a load by the operation of cylinder 90. This permits a load to be picked up without the wheels of 'the truck traversing the earth around the building under construction and to be placed in a door, window or other opening, or on-a platform at a level substantially above the height of the truck. I

In, the operation of an extended reach truck having the lift mechanism described herein, starting with the fork attachment in its lowered position, the operator moves the truck forwardly to slip the tines of the fork attachment under a load, and lifts the load from the ground. Normally the attachment is operated by cylinder 76 to tilt the load rearwardly and/or to lift it a short distance from the ground. Cylinders 100 are then normally operated to lift the load sufficiently from the ground to effectively clear the area to be traversed by the truck. The truck is then maneuvered to the position where the load is to be displaced such as, forexample, on the platform of a scaffold, and cylinder assemblies 80 and 100 are operated to lift the load in a substantially vertical line to the platform. When the load is on a level with the upper surface -or slightly above the A compensating mechanism such as the hydraulic system indicated generally by numeral 180 in copending U.S. Pat. application Ser. No. 221,346, filed Jan. 27, 1972, and owned by a common assignee, can be incorporated in the present extensible reach mechanism to prevent drooping of the load on the attachment and, under certain operating conditions, to maintain the movement of the boom and load on a horizontal plane. When the compensating mechanism is used in conjunction with the extensible and contractable posts, an adjustment means such as a hydraulic cylinder which extends and contracts with cylinder 80, maintains the mechanism in proper relationship with the posts and boom regardless of any temporarily adjusted length of the posts. The compensation 'for droop, however, can be performed entirely by the manual controls if desired.

While only one embodiment of the present dual extensible reach mechanism for a lift truck has been described in detail herein, various changes and modifications may be made without departing from the scope of the invention.

I claim:

1. An extensible reach mechanism for a truck having a frame with a forward end and a rearward end, comprising a telescoping extensible and retractable post pivotal in either direction from a substantially vertical position, at its lower end to the rear end of the truck frame, a boom pivotally connected to the upper-end of upper surface of the platform, cylinder 90 is operated to move attachment 60 and the load thereon onto the platform. Cylinder 100 is then lowered sufficiently to place the load on the platform, and cylinder 90 is operated to withdraw the attachment from the load and the platform. Cylinders 80 and 100 are operatedby separate and independent controls so that the load can be maneuvered effectively, either by raising the boom upwardly or downwardly while maintaining it on a substantially horizontal plane, or one cylinder may be moved while holding the other cylinder fixed, thereby pivoting the boom at the center or at the rear end, de pending upon which of the two cylinders is moved. The tines of the attachment are maintained'on a substantially horizontal plane by cylinder 76 as the boom is moved from the position shown in full lines in FIG. 2 to the position shown in broken lines.

It is seen from the. foregoing that the present extended reach mechanism places a substantial part of the mechanism near the rear of the vehicle, thus counterbalancing at least a portion of the load attachment- 60 and at the same time giving the driver a good forward view and a good view of the load and the attachment, so that the truck can be easily maneuvered and the lift mechanism can be operated effectively to place the load in any desired elevated position, without interference from any upright or other mechanism which could seriously obscure the view. The mechanism permits the load to be readily placed in any desired location on a scaffolding platform or through an elevated door or window of the building being constructed, without requiring the truck to move directly beneath the scaffolding or building wall and without requiring special handling of the load.

said post and extending toward the forward end of the truck frame, a load carrying attachment connected to and adjustable relative to the forward end of said boom, a power means connected to said post for pivoting said post forwardly and rearwardly to move said boom and load attachmentforwardly and rearwardly, an extensible and retractable leg spaced forwardly from said post for pivoting said boom upwardly ariddownwardly to raise and lower the forward end of said boom and thereby. to'elevate-and lower said load attachment, said leg forming a fulcrum for said boom when said post is extended or retracted independently of or at a different rate from said power means.

2. An extensible reach mechanism for a truck as defined in claim 1 in which said leg and said power means include hydraulic cylinders.

3. An extensible reach mechanism for a truck as defined in claim 1 in-which a pair of said posts and a pair of said second legs-support and operate said boom, and said posts and second power means include hydraulic cylinders.

4. An extensible reach mechanism for a truck as defined in claim 1 in which a hydraulic cylinder is connected to said load attachment and to said boom to position said attachment angularly with respect to said boom.

5. An extensible reach mechanism for a truck as defined in claim 1 in which said leg is spaced further from said post at the top than at the bottom, and said boom includes a downwardly extending portion to facilitate lowering said load carrying attachment to a point below the level of the ground on which the truck is supported.

6. An extensible reach mechanism for a truck as defined in claim 3 in which said leg is spaced further from said post at the top than at the bottom and said boom includes a downwardly extending portion to facilitate lowering said load carrying attachment to a point below the level of the ground on which the truck is supported.

7. An extensible reach mechanism for a truck, extensible and a telescoping and retractable pivotal in either direction from a substantially vertical position and connected at its lower end to the truck near one end thereof, a boom structure pivotally connected to the upper end of said vertical member and extending toward the other end of the truck, a load carrying attachment connected to and adjustable relative to said other end of the boom structure, a power means connected to said vertical member for pivoting said vertical member forwardly and rearwardly and moving said boom structure and load attachment forwardly and rearwardly, and an extensible and retractable leg for pivoting said boom structure upwardly and downwardly to raise and lower the forward end of said boom structure and thereby to elevate and lower said load attachment either separately from or in unison with said extensible and retractable vertical member.

8. An extensible reach mechanism for a truck as defined in claim 7 in which said power means and leg include hydraulic cylinders, and in which a source of hydraulic fluid under pressure and a pair of valve means control the operation of said cylinders.

9. An extensible reach mechanism for a truck as defined in claim 7 in which a hydraulic cylinder is connected to said load attachment and to said boom to position said attachment angularly with respect to said boom.

10. An extensible reach mechanism for a truck as defined in claim 8 in which a hydraulic cylinder is connected to said load attachment and to said boom to position said attachment angularly with respect to said boom.

1 1. An extensible reach mechanism for a truck as defined in claim 7 in which a pair of said posts and a pair of said second legs support and operate said boom, and said posts and second power means include hydraulic cylinders.

UNITED STATES PATENT @FFKCE CERTIFICATE CF CECTWN O PATENT NO. 3,802,589

DATED April 9, 1974 INVENTOR(S) 1 Donald A. Holtkamp It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE SPECIFICATION Column 1: Line 22, change "result" to ==results-;

Line 33, change "wheel" to --wheels-=, Column 3: Line 15, change "forks" to --tines; Line 52, change "described" to -desired--;

Line 61, change "deliveres" to =-delivers---,

Column 4: Line 10, change "142" to -l40--;

Line 44, change "cylinder 82" to -==-cylinder assembly 80 Line 54, change "he" to -==-the--; Line 58, before "line 186" insert --with-- 0 Column 5: Line 3, after "boom" change "of" to -on- Line 29, change "displaced to --==discharged-=,

IN THE CLAIMS Column 6: Claim 1, line 28, after "position" delete the comma and insert and connected-;

line 42, change "power means" to -=-leg-.

Column 7: Claim 7, line 2, after "truck" insert -'comprising v a telescoping=--; line 3, delete "and a telescoping" and after "retractable" insert membert he a? third ay 0? February 1976 e [SEAL] Attest:

RUTH C. MASON r3. MARSHALL DANN Arresting Officer Commissioner ofParents and Trademarks Q 

1. An extensible reach mechanism for a truck having a frame with a forward end and a rearward end, comprising a telescoping extensible and retractable post pivotal in either direction from a substantially vertical position, at its lower end to the rear end of the truck frame, a boom pivotally connected to the upper end of said post and extending toward the forward end of the truck frame, a load carrying attachment connected to and adjustable relative to the forward end of said boom, a power means connected to said post for pivoting said post forwardly and rearwardly to move said boom and load attachment forwardly and rearwardly, an extensible and retractable leg spaced forwardly from said post for pivoting said boom upwardly and downwardly to raise and lower the forward end of said boom and thereby to elevate and lower said load attachment, said leg forming a fulcrum for said boom when said post is extended or retracted independently of or at a different rate from said power means.
 2. An extensible reach mechanism for a truck as defined in claim 1 in which said leg and said power means include hydraulic cylinders.
 3. An extensible reach mechanism for a truck as defined in claim 1 in which a pair of said posts and a pair of said second legs support and operate said boom, and said posts and second power means include hydraulic cylinders.
 4. An extensible reach mechanism for a truck as defined in claim 1 in which a hydraulic cylinder is connected to said load attachment and to said boom to position said attachment angularly with respect to said boom.
 5. An extensible reach mechanism for a truck as defined in claim 1 in which said leg is spaced further from said post at the top than at the bottom, and said boom includes a downwardly extending portion to facilitate lowering said load carrying attachment to a point below the level of the ground on which the truck is supported.
 6. An extensible reach mechanism for a truck as defined in claim 3 in which said leg is spaced further from said post at the top than at the bottom and said boom includes a downwardly extending portion to facilitate lowering said load carrying attachment to a point below the level of the ground on which the truck is supported.
 7. An extensible reach mechanism for a truck, comprising a telescoping extensible and retractable member pivotal in either direction from a substantially vertical position and connected at its lower end to the truck near one end thereof, a boom structure pivotally connected to the upper end of said vertical member and extending toward the other end of the truck, a load carrying attachment connected to and adjustable relative to said other end of the boom structure, a power means connected to said vertical member for pivoting said vertical member forwardly and rearwardly and moving said boom structure and load attachment forwardly and rearwardly, and an extensible and retractable leg for pivoting said boom structure upwardly and downwardly to raise and lower the forward end of said boom structure and thereby to elevate and lower said load attachment either separately from or in unison with said extensible and retractable vertical member.
 8. An extensible reach mechanism for a truck as defined in claim 7 in which said power means and leg include hydraulic cylinders, and in which a source of hydraulic fluid under pressure and a pair of valve means control the operation of said cylinders.
 9. An extensible reach mechanism for a truck as defined in claim 7 in which a hydraulic cylinder is connected to said load attachment and to said boom to position said attachment angularly with respect to said boom.
 10. An extensible reach mechanism for a truck as defined in claim 8 in which a hydraulic cylinder is connected to said load attachment and to said boom to position said attachment angularly with respect to said boom.
 11. An extensible reach mechanism for a truck as defined in claim 7 in which a pair of said posts and a pair of said second legs support and operate said boom, and said posts and second power means include hydraulic cylinders. 